Invasive Giant Rats Make a Comeback in the Florida Keys

By Terrell Johnson

Published Jun 3 2014 08:30 PM EDT

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Florida wildlife officials are still on the hunt for a creature that, despite intensive efforts to eradicate it for nearly a decade, is holding its own on Grassy Key, an island in the middle of the Florida Keys.

Native to central and southern Africa, the Gambian giant pouch rat was imported to the United States as an exotic pet for years until 2003, when the federal government banned them after an outbreak of monkey pox among the species.

In the late 1990s, a pet breeder released about a half-dozen Gambian rats that had been kept as pets into the wild on Grassy Key. Whether it was accidental or intentional, nobody knows for sure, but the rat quickly established a reproducing population, which mushroomed in the years since.

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In 2007, officials with the Florida Fish and Wildlife Commission began extensive efforts to remove the rats – which average about 3 pounds in size, but can grow up to 3 feet long and weigh up to 9 pounds, making them the world's largest rat – from Grassy Key. The rats proved resilient, however, and seven years later officials are still trying to kill off the last of them.

"We know that there are still some out there and we've been doing some limited trapping and monitoring,” Jenny Eckles, a non-native wildlife biologist with the commission, told the Miami Herald.

"We're also hiring [the U.S. Department of Agriculture] to come back down and do 10-day trappings," she added in the interview this weekend. "They'll trap four times over the next year for 10 days each."

They'll need to work quickly. Gambian rat females can have as many as five litters in nine months, with an average of four offspring in each litter, according to Florida Fish & Wildlife officials. They've also reportedly made their way from Grassy Key and onto nearby Key Largo, and have also been spotted in nearby Marathon.